A conventional test and measurement system, such as a signal measurement system, typically provides a display grid commonly referred to as a graticule on which display elements are presented. The display grid divides the coordinate axes into a series of divisions. Waveforms are displayed on the graticule and are scaled vertically and horizontally to facilitate analysis. Typically, the horizontal scale represents sweep speed and is in units of seconds per division. The vertical scale represents signal amplitude and is in units of volts per division. A captured waveform or trace is stored as trace data in a memory of the signal measurement system for display. With ever increasing depth (number of acquired samples) of the signal measurement system, the amount of trace data can become far too large to display on the display screen. As a result, a user is only able to meaningfully view a small portion of the trace data at any one time. It is thus important for the user to know at least the location of the displayed portion within the trace so as to be able to select or navigate to a different portion of the trace.
One prior art signal measurement system that includes such a feature is disclosed in the U.S. Pat. No. 6,559,868, Alexander, entitled “Graphically relating a Magnified View to a simultaneously displayed Main View in a signal measurement system”. FIG. 1 shows a display screen 2 of the signal measurement system prior to the invocation of a waveform magnification feature. The display screen 2 shows a memory bar 4 and a main waveform display 6A. The main waveform display 6A displays only a portion 8 of a trace stored in memory. Displayed in the memory bar 4 is a dummy waveform 10 that does not reflect the actual trace. The memory bar 2 includes a main selection window 12 therein that indicates the portion 8 of the trace that is currently displayed in the main waveform display 6A. Since the memory bar 2 does not show the actual trace, the operator is unable to know which portion of the trace is of interest and will need to navigate the entire trace to locate a desired portion.
When the waveform magnification feature is invoked, a further magnified waveform display 14 is provided as shown in FIG. 2. The display screen 2 is partitioned into a reduced-size main waveform display 6B and the magnified waveform display 14. The main waveform display 6B is now allocated a portion 16 of the display screen 2 while the magnified waveform display 14 is drawn in the portion 18 of the display screen 6 not occupied by the main waveform display 6B. The main waveform display 6B presents a selected portion 8 of the entire trace as described above. The magnified waveform display 14 presents a predetermined or selected portion 19 or region of the waveform portion 8 in the main waveform display 6B at some expanded scale. Such a magnified view of a desired region 19 of the displayed waveform portion 8 allows an operator to easily and accurately determine relative values between the waveform portion 8 and other displayed waveforms (not shown). The magnified view is also a useful and productive technique for displaying details of a displayed waveform portion 8 to better understand the behavior of the waveform portion 8 and its correlation with measured quantities such as peak-to-peak voltage, rise-time, etc. With the availability of both the main waveform display 6B and the magnified waveform display 14, more details of the trace are now displayable to make navigation easier than before.